Bixing is the traditional expression of China's poetry. In the Song Dynasty, Zhu regarded Bixing as an expression to explain its basic characteristics. He thinks: "If you compare, you should compare with other things"; "Monkey, let's say something else to make the lyrics sung." Generally speaking, comparison is a metaphor, a metaphor that visualizes people or things, making its characteristics more distinct and prominent. Some poems are partial comparisons, and some are overall image comparisons, just like poems describing objects in later generations; "Xing" means rising, that is, using other things as the starting point of poetry to arouse the content to be praised. Some "Xing" has the dual functions of origin and metaphor, so the word "Bi Xing" is often used to refer to the meaning of poetry.